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Article contents:== breadline [[toc:]] === Introduction This egg provides an incomplete set of bindings to the [[http://tiswww.case.edu/php/chet/readline/rltop.html|GNU Readline]] library, suitable for augmenting {{csi}} and writing a {{csi}}-like application with line editing support. See [[https://depp.brause.cc/breadline/examples|the bundled examples]] for a {{.csirc}} providing Scheme completion. === Author Vasilij Schneidermann === Repository [[https://depp.brause.cc/breadline]] === Current state of the bindings * Basic interface for reading input and managing history * Completion interface * Text manipulation * Redisplay and event hooks * Customization of aspects crucial for Scheme programming === Requirements You'll need to have a not too old version of GNU Readline installed. This egg has been tested with version 7, but version 6 should work as well. In case the auto-detected flags don't work for you, make sure to set {{READLINE_CFLAGS}} and {{READLINE_LDLIBS}} before installation. The following subsections show known workarounds for platforms where the default build script does not suffice: ==== Ubuntu 18.04 export READLINE_CFLAGS=-I/usr/include/readline export READLINE_LDLIBS=-lreadline chicken-install breadline An alternative solution is to set up {{/usr/share/pkgconfig/readline.pc}} as described on [[https://www.marache.net/post/readline-pc.html|Simon Marache-Francisco's blog]]. Edit the file to contain the following, then run {{chicken-install breadline}}: Name: Readline Description: Gnu Readline library for command line editing URL: http://tiswww.cwru.edu/php/chet/readline/rltop.html Version: 7.0 Requires.private: tinfo Libs: -lreadline Cflags: -I/usr/include/readline ==== macOS Homebrew Ensure that {{pkg-config}} and {{readline}} have been installed via Homebrew. Consider Homebrew's remarks after installing readline: readline is keg-only, which means it was not symlinked into /usr/local, because macOS provides BSD libedit. For compilers to find readline you may need to set: export LDFLAGS="-L/usr/local/opt/readline/lib" export CPPFLAGS="-I/usr/local/opt/readline/include" For pkg-config to find readline you may need to set: export PKG_CONFIG_PATH="/usr/local/opt/readline/lib/pkgconfig" Therefore export all of these, then run {{chicken-install breadline}}. In case it still doesn't work and {{pkg-config --libs readline}} fails, this may be the fault of an incorrect {{readline.pc}} file, see [[https://github.com/Homebrew/homebrew-core/issues/38972|Homebrew's issue tracker]] and update. ==== mingw-msys2 Assuming a 64bit installation, the egg can be installed as follows: pacman -S pkg-config mingw-w64-x86_64-readline export READLINE_CFLAGS=$(pkg-config --cflags readline) export READLINE_LDLIBS=$(pkg-config --libs readline) chicken-install breadline === API ==== History <procedure>(history-length)</procedure> Returns the current history length. <parameter>(history-file)</parameter> <parameter>(history-file PATH)</parameter> Specifies the location of the history file for {{make-readline-port}}. Defaults to {{#f}} which means to neither read nor write out the history. {{PATH}} may be relative to the current working directory. <procedure>(add-history! ITEM)</procedure> Adds {{ITEM}} to the current history. <procedure>(read-history! FILE)</procedure> Reads in history items from {{FILE}} and adds them to the current history. <procedure>(write-history! FILE)</procedure> Writes out current history items to {{FILE}}. <procedure>(stifle-history! MAX)</procedure> Configure the current history to hold at most {{MAX}} items. <procedure>(unstifle-history!)</procedure> Undo any history stifling. Returns the previously set maximum amount of history items as set by {{stifle-history!}}. If the history was not stifled before, the value is negative. ==== Completion <procedure>(completer-set! PROC)</procedure> Set the completion handler to {{PROC}}. {{PROC}} is called repeatedly to collect completions with a fixnum state argument and a string prefix. A state argument of zero means that the completion procedure may initialize its data, it is incremented for every subsequent call. The completion procedure must either return a completion matching the given string prefix or {{#f}} to signal that no further completions follow. It is up to the completion procedure to keep track of what completions have been offered and whether any further completions are vailable. <procedure>(completer-word-break-characters-set STRING)</procedure> Sets the word-breaking characters for completion to {{STRING}}. The default value of {{\t\n\"\\'`@$><=;|&{(}} is suitable for Bash's completion. ==== Text Manipulation <procedure>(line-buffer)</procedure> Returns a string representing the current line contents. <procedure>(point)</procedure> <procedure>(end)</procedure> Returns a number representing the position of point and end of the line. If point is at the end of the line, point and end are equal. <procedure>(display-prompt)</procedure> Returns a string representing the current prompt. This is usually identical to the prompt strings, but may differ from them, for example when performing incremental search. <procedure>(insert-text STRING)</procedure> Insert {{STRING}} into the line at the current cursor position. Returns the number of characters inserted. <procedure>(delete-text START END)</procedure> Delete the text between {{START}} and {{END}} in the current line. Returns the number of characters deleted. <procedure>(stuff-char CHAR)</procedure> Insert {{CHAR}} into the Readline input stream. It will be "read" before Readline attempts to read characters from the terminal. Up to 512 characters may be pushed back. Returns {{1}} if the character was successfully inserted; {{0}} otherwise. ==== Redisplay <procedure>(redisplay)</procedure> Change what's displayed on the screen to reflect the current contents of Readline's buffer. <procedure>(redisplay-function-set! PROCEDURE)</procedure> Sets a function that will be called periodically when Readline performs redisplay. The argument should be a thunk. Its return value is ignored. The default behavior may be enabled by passing {{#f}}. ==== Event hooks <procedure>(event-hook-set! PROCEDURE)</procedure> Registers a hook that will be called periodically when Readline is waiting for terminal input. By default, this will be called at most ten times a second if there is no keyboard input. The argument should be a thunk. Its return value is ignored. Only one event hook may be registered at a time. A previously-registered hook may be disabled by passing {{#f}}. <procedure>(pre-input-hook-set! PROCEDURE)</procedure> Registers a hook that will be called every time the first input prompt has been printed, just before {{readline}} starts reading input characters. The argument should be a thunk. Its return value is ignored. Only one pre-input hook may be registered at a time. A previously-registered hook may be disabled by passing {{#f}}. ==== Customization <procedure>(variable-bind! VARIABLE VALUE)</procedure> Sets a GNU Readline variable to a value. Both {{VARIABLE}} and {{VALUE}} must be strings. <procedure>(variable-value VARIABLE)</procedure> Retrieves the current value of the given GNU Readline variable. {{VARIABLE}} must be a string. <procedure>(basic-quote-characters-set STRING)</procedure> Sets the quoting characters to {{STRING}}, the default value being {{"'}}. This setting is used for paren blinking to determine strings. <procedure>(paren-blink-timeout-set MICROSECS)</procedure> Sets the timeout for paren blinking in microseconds, the default value being 500000 microseconds. Note that typing a closing paren will not blink the opening paren unless {{blink-matching-paren}} has been set. ==== Line editing <procedure>(readline PROMPT)</procedure> Read in a line of user input after printing {{PROMPT}}. Returns the user input or {{#f}} if input has been terminated with {{C-d}}. <procedure>(make-readline-port [PROMPT])</procedure> Returns an input port using GNU Readline for line editing and history management. {{PROMPT}} may be a string or a thunk returning a string and defaults to {{(repl-prompt)}}. ==== Cleanup <procedure>(cleanup-after-signal!)</procedure> <procedure>(reset-after-signal!)</procedure> Procedures to call in sequence after receiving a signal in a signal handler to ensure a clean terminal and readline state. <procedure>(reset-terminal! [TERMINAL-NAME])</procedure> Procedure to call after program exit to ensure a clean terminal state. The optional argument {{TERMINAL-NAME}} defaults to the value of the {{TERM}} environment variable. === Examples <enscript highlight="scheme"> (import (chicken process signal)) (import breadline) (set-signal-handler! signal/int (lambda _ (cleanup-after-signal!) (reset-after-signal!))) (on-exit reset-terminal!) (let loop () (let ((input (readline "> "))) (if input (begin ;; processing code goes here (print input) (add-history! input) (loop)) (newline)))) </enscript> Further examples for usage in {{csi}} and writing your own completer can be found [[https://depp.brause.cc/breadline/examples|in the repository]]. === License Copyright 2016 Vasilij Schneidermann This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. A full copy of the GPL license can be found at <http://www.gnu.org/licenses/>. === Version history ==== 0.12 * Fix Scheme completions code to not error out on CHICKEN 5.4.0 ==== 0.11 * Make {{event-hook-set!}} and {{pre-input-hook-set!}} only set the hook when using the functions and unset it when passing {{#f}}. This resolves a segfault in a readline port while pressing complex key sequences. ==== 0.10 * Introduce {{line-buffer}}, {{point}}, {{end}}, {{display-prompt}} and {{redisplay-function-set!}} to allow for syntax highlighting. ==== 0.9.1 * Abort build on non-zero exit ==== 0.9 * Make use of callback-based interface to handle interrupts graciously (thanks Evhan!) ==== 0.8 * Expose cleanup procedures for signal and exit handlers * Make use of these procedures in examples ==== 0.7 * Quote user-provided environment variables in Windows build script * Add build instructions for Ubuntu 18.04 and mingw-msys2 ==== 0.6 * Change build script to use Scheme when possible * Improve examples ==== 0.5 * Improve pkg-config check ==== 0.4 * Use custom build script trying to use pkg-config, then falling back to {{CFLAGS}} and {{LDFLAGS}} ==== 0.3 * Support thunks for make-readline-port and its prompt (thanks Marco Maggi!) * Expose history-length procedure (thanks Marco Maggi!) ==== 0.2 * Link explicitly against ncurses (thanks Marco Maggi!) * Expose event and pre-input hooks and text modification functions (thanks Evhan!) ==== 0.1 * Initial release Description of your changes:

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